Learn Hardcore Turkish: Babam, yarın yağmur yağacağını duymuş. - My father has heard that it will rain tomorrow.

Duydu = he/she heard (plain past fact, the speaker presents it as known or witnessed)
Duymuş = he/she has heard / apparently heard / I hear that he heard

So Babam … duymuş suggests:

the speaker did not directly witness the act of hearing, and/or
the information is new, reported, or slightly distant from the speaker.

A natural English translation is something like:

My father has heard that it will rain tomorrow.
Apparently my father heard that it will rain tomorrow.

Why does Turkish say yağmur yağacağını (literally “rain will rain”)? Isn’t that redundant?

In Turkish, the usual way to say “it rains / it will rain” is the expression yağmur yağmak, literally “rain falls”.

yağmur = rain (noun)
yağmak = to fall (for rain, snow, etc.)

So:

Yarın yağmur yağacak. = It will rain tomorrow. (literally: Tomorrow rain will fall.)

When you turn this into a noun clause (so that it can be the object of duymak = to hear), the whole phrase yağmur yağacak becomes yağmur yağacağını = “that it will rain”.

It feels redundant in literal English, but in Turkish it’s just the normal idiom for talking about rain.

Why do we say yağmur yağacağını instead of just yağmur yağacak after duymuş?

Because after duymak you need a “that‑clause” which functions like a noun, not an independent sentence.

Independent sentence:
Yarın yağmur yağacak. → It will rain tomorrow.
Noun clause (object of duymak):
yarın yağmur yağacağını → that it will rain tomorrow

In Turkish, to make a clause into a noun phrase, you:

Put the verb in a special -acak/-ecek form plus possessive,
And usually mark it with accusative -ı/i/u/ü if it is a direct object.

So:

Babam, yarın yağmur yağacak duymuş. ❌ feels ungrammatical;
Babam, yarın yağmur yağacağını duymuş. ✅ correct:
My father has heard that it will rain tomorrow.

An alternative way is to use diye:

Babam, yarın yağmur yağacak diye duymuş.
Literally: He heard as “it will rain tomorrow”.
This is also correct and colloquial, but the version with yağacağını is the classic noun‑clause structure.

How is the form yağacağını built? What are the parts?

Breakdown of yağacağını:

yağ- → verb stem (yağmak = to fall, to rain)
-acak → future tense/participle suffix
yağ- + -acak → yağacak = will rain
When we add a vowel‑initial suffix to -acak, the k → ğ change happens: yağacak + -ı → yağacağı
-ı → 3rd person singular possessive marker (its / his / her)
This is part of forming a noun clause.
-nı → accusative case ending, with buffer -n-

So:

yağ- + -acak + -ı + -nı
= yağacağı + nı
= yağacağını

Functionally, yağacağını means “that it will rain” and behaves as a noun phrase (the thing that is heard).

Where is the subject of the embedded clause? Shouldn’t it be yağmurun somewhere?

The hidden full form of the embedded clause is:

Yarın yağmurun yağacağı → that the rain will fall tomorrow.

In a typical noun clause with -acak/-ecek:

The subject of the embedded clause is in genitive (like a kind of possessive),
The verb has a possessive suffix.

Example with a person:

Ahmet’in geleceğini duydum.
I heard that Ahmet will come.
(Ahmet’in = genitive subject; geleceğini = “his coming / that he will come”)

With yağmur the fully explicit form is:

Babam, yarın yağmurun yağacağını duymuş.
My father has heard that it will rain tomorrow.

In actual speech, when the meaning is clear, the genitive subject (yağmurun) is often dropped:

Babam, yarın yağmur yağacağını duymuş.

So the subject is effectively yağmur, but the genitive -un is omitted in this everyday form.

Is Babam yarın yağmur yağacağını duymuş different from Babam yarın yağmurun yağacağını duymuş?

Grammatically:

Babam yarın yağmur yağacağını duymuş.
Babam yarın yağmurun yağacağını duymuş.

Both are correct and have the same basic meaning:
My father has heard that it will rain tomorrow.

Nuance:

With yağmurun, the sentence is more formally complete, matching the classical rule of genitive subject + possessive verb in noun clauses.
Without -un, it is more colloquial / relaxed. Native speakers very often omit this -un when there is no ambiguity.

In this particular sentence, the difference is tiny; both versions are natural.

What is the word order rule here? Could we move yarın or yağmur around?

Turkish word order is flexible, but the default is:

Subject – Time – (Other details) – Object – Verb

Your sentence follows that pattern:

Babam (subject)
yarın (time)
yağmur yağacağını (object clause)
duymuş (main verb)

Possible variations (all grammatical, with slight shifts in emphasis or style):

Babam yağmurun yarın yağacağını duymuş.
(emphasizes the time a bit differently)
Yarın babam yağmur yağacağını duymuş.
(puts yarın as the scene‑setting word first)
Babam, yağmurun yarın yağacağını duymuş.

The one element that must stay at the end is usually the main verb (duymuş). Inside the embedded clause, yağacağını is also at the end of that mini‑clause.

Why do we use a future form (yağacağını) with a past form (duymuş)?

Because the two verbs refer to different times:

duymuş → the hearing happened in the past (relative to now).
yağacağını → the rain is expected to happen in the future (relative to that past moment, or relative to now).

English does the same thing:

He heard that it would rain.
He has heard that it will rain.

Turkish:

Babam, yarın yağmur yağacağını duymuş.
My father has heard that it will rain tomorrow.

So the tense of the main verb (duymuş) shows when he heard it, and the tense inside the embedded clause (yağacağını) shows when the rain is supposed to happen.

Could we say Babam yarın yağmur yağacakmış instead? What is the difference?

Yes, and there is a subtle difference:

Babam, yarın yağmur yağacağını duymuş.
Literally: My father has heard that it will rain tomorrow.
– Focus: My father heard it from somewhere.
Babam, yarın yağmur yağacakmış.
Literally: Apparently it will rain tomorrow, my father says / I heard from my father.
– Main verb: yağacakmış (reported future of “it will rain”)
– Babam now functions more as the source of that information.

Sentence 1:

Reports the action of hearing done by your father.

Sentence 2:

Reports the content of the information (that it will rain),
And marks this content as reported/hearsay (from your father) using -miş on the inner verb.

Both involve reported information, but in different places:

In (1), the hearing is reported (duymuş).
In (2), the future event (rain) is reported (yağacakmış).

How would I say “My father heard that it rained yesterday”?

Here the rain is in the past, so you need a past‐tense noun clause:

Babam, dün yağmur yağdığını duymuş.

Breakdown:

dün = yesterday
yağdı = it rained
yağdığını = that it rained (past noun clause form)
duymuş = has heard / apparently heard

You could also use duydu instead of duymuş if you don’t want the evidential nuance:

Babam, dün yağmur yağdığını duydu.
My father heard that it rained yesterday. (plain past statement)

If I remove yarın, does anything else in the sentence have to change?

No structural change is needed. You simply lose the time information:

Babam, yarın yağmur yağacağını duymuş.
My father has heard that it will rain tomorrow.

→ remove yarın:

Babam, yağmur yağacağını duymuş.
My father has heard that it will rain. / My father has heard that it’s going to rain.

Everything else (yağmur yağacağını duymuş) stays exactly the same.

Can duymuş here also imply surprise or “I’ve just found this out”?

Yes. The -miş past (duymuş) often carries one or both of these nuances:

Reported / indirect information
– you got the information from someone else, not from direct observation.
New or unexpected information for the speaker
– like: “Oh, it turns out that …”, “I’ve just learned that …”.

So Babam, yarın yağmur yağacağını duymuş can sound like:

It turns out my father has heard that it will rain tomorrow.
Apparently my father heard that it will rain tomorrow.

Context and intonation decide how strong the surprise / newness feeling is, but that nuance is available with -miş.